1. Field of the Invention
The present invention relates to an image encrypting method and device for encrypting an image and performing an image processing such as image synthesis on the encrypted image, a recording medium on which image encrypting procedures are recorded, and a recording medium on which an encrypted image file is recorded.
2. Description of the Related Art
Methods of encrypting such as disclosed in Japanese Patent Application Laid-Open (JP-A) No. 5-199424 or Japanese Patent Application Laid-Open (JP-A) No. 6-125553 have been known as conventional encrypting methods. JP-A-5-199424 describes a simple technique for a public key system or a common key system as a conventional encrypting method, and as another encrypting method, proposes a method in which an image is encrypted by changing the order of permutations of image blocks.
In JP-A-6-125553, a method of encrypting a portion of the image is proposed because encrypting of the entire image results in a large load. However, there is a slight decrease in reliability in the encrypting of a portion of the image as compared to the encrypting of the entire image. Accordingly, there are cases in which the entire image should be encrypted.
When the entire image is encrypted, naturally, the contents of the encrypted image data cannot be recognized by a device which is not authorized to decrypt.
For example, when an image server and an operator (image operator) are connected to each other via a network, in the case in which the image server does not have the authorization to decrypt and only the operator is authorized to decrypt, there is no method other than transmitting all of the image data, even if the operator requires only a portion of the image (e.g., a divisional tile when the image is divided into a grid, the resolution, or the like).